Camera with adjusting device for objective lens and image carrier and a focusing process

ABSTRACT

A camera is described with objective lens and image reception carrier equipment and a focussing process. From related extension measured distances (x1-x2, x2-x3, δb), final adjusted, set-point focus values (θ soll , Φ soll ) are obtained in the course of the focussing of various image points (B1, B2, B3) for a multiply pivotable, bellows camera which produces the pivoting angles (α, β, θ, Φ), the latter used for a double focussing compensation; by this means, the direct making of an exact spatial interval distance measurement between the objective lens carrier (OT) and the and image carrier (BT) is dispensed with, since at least a relatively accurate extension measurement (δb) at a predetermined objective lens setting is obtained and evaluated. 
     The optical bench (OB) can be equipped with a raster arrangement for the image carrier (B1), the objective lens carrier (OT) and be constructed in sections (OB1, OB2).

The invention concerns a focusing process for a camera, said camera:

having an objective lens carrier and an image carrier, which aremaintained positionally relative to one another in a straight lineoptical bench direction in which the spatial interval between them isvariable, wherein the said interval changes are signaled to amicroprocessor,

being equipped with an objective lens carrier and an objective lenssecured to pivot about two axes, said axes being vertical to one anotherand to an optical bench, the two respective objective lens angles andthe focal length of said lens being input to a processor,

possessing an image carrier in which an image screen, namely a frostedglass plate is secured, which screen is moveable about two axesvertically disposed to one another and to the direction of the bench,the two respective image reception angles being sent to the processor,

having in the image screen, a focusing adjustment sensor, which signalsa degree of focus, and is positionable in two image receptioncoordinates which, together with the focus value, are conducted to theprocessor,

further possessing at least three select image point areas, which lie ina secondary image plane for the simultaneous adjustment of the focus,

having these said image point areas on the image screen subjected todetermination of their respective image screen coordinates by means of achange in the interval between the image carrier and the objective lenssequentially for each area through focus adjustment, and the saidpositional changes of the image carrier are input to the processor,

obtaining, by means of the input data so collected, from the processorcomputer a determination of the positional parameters of the imagescreen as well as of the secondary image from which, together with afurther image parameter necessary for computation, this latteroriginating in the solution of image equations, there will be calculatedfixed adjustment values suitable for the pivoting of the objective lenscarrier along with a value for the adjustment of the interval betweenthe carriers of the image and the objective carrier, the results thereofbeing made available, so that the new image plane adjusted by theseset-point values comes as close as possible to coinciding with the imagescreen.

A camera of this type is brought into common knowledge by DE 34 33 412C2. In this case,

the objective lens focal length,

an image scale, based on

the spatial coordinates of the three select real image point areas,which were determined from the optical imagery of a scale of the image,to which purpose a focus sensor serves as an aid,

the angle adjustment of the objective lens and image screen inclinationsand degrees of deviation,

and the spatial interval between the principal plane of the objectivelens to the image screen,

are either input to the processor by a keyboard or provided direct withmeasured values.

From these data the processor computes the set point signal for theadjustment angle and the said interval. In this computation, theprocessor makes use of the Law of Scheimpflug according to which, theobjective lens plane, the plane to which the real image belongs and theplane to which the focused image points belong, must mandatorilyintersect in one straight line.

Thus, in accord with a preset adjustment, the selected image point areaof the real subject, by means of the so called double focuscompensation, is imaged as sharply as possible. With this apparatus, inaddition the absolute space coordinates of the image points and thestructural data of the imagery optics are required as starting pointvalues for a final solution of the image equations. This is in order tofind such a position of the image screen in relation to the setting ofthe objective lens, that the select image point areas lie with thesharpest possible focus in the image screen. This requires a substantialarray of means of measurement having high requirements as to precision.Moreover, the Law of Scheimpflug, which was employed, is valid only forthe imagery in a paraxial zone of a thin lens, making it of littlemeaning in practice.

Thus, it is the purpose of the invention, to achieve an automatic focusadjustment of a real image, using the camera described in theintroductory passages, employing double focus compensation with thereduced demand for measurement equipment, simplified apparatus and anobjective lens acceptable in practice.

The accomplishment of this purpose lies therein, in that one of theobjective lens adjustment parameters can be altered in given quantity,and as this is carried out, for a selected image point, the extensiondifference of a extension adjustment apparatus lying between its twofocus adjustments in the bench direction, is measured. This brings abouta first set of the of the image equations by the use of the originalobjective lens adjustment parameters and an undetermined image distance,and a further set of image equations with the inclusion of the nowvaried objective lens adjustment parameters and the undetermined imagedistance. These two sets are equalized for the image distance as alteredby the extension difference and solved for the set-point adjustmentvalues. Another approach to solution is the functional derivation of theimage comparisons with reference to the objective lens positionalparameters and involving the prior adjustment changes made from time totime along with the measured extension difference, all included in thesaid derivations, and, in accord with the set-point parameters, solvingfor the said undetermined object distance.

Advantageous embodiments are described in the subordinate claims.

The new process renders the absolute distant measurement between theobjective lens carrier and the image carrier superfluous. It nowsuffices, that the respective angular measurement equipment is at handand the relative measurement of the interval, that is, the extensionchanges in the course of the various focus placements, as well as thecoordinate determinations on the screen, are to be available.

The adjustment process may be summarized in the following sequence ofoperations:

The photographer adjusts the perspective by deflecting the screen andsubsequently carries out a rough pre-focusing of the image. He does thisgenerally through altering the extension and in some cases by tiltingthe objective lens. The parameters "a_(m) " and "b_(m) " of the screen,which determine its normal vector, but not, however, its distance fromthe objective lens, which is not necessary here, as well as the adjusteddeflection angles θ_(o) and Φ_(o) of the objective lens are read off bythe built-in goniometer in the computer.

The determination of the coordinates bi=(xi, yi, zi) from at least threeimage points by means of focusing is done with the aid of a CCD-sensor(or the equivalent thereof); meanwhile, the camera objective lens isswivelled through the angles θ_(o) and Φ_(O). The X-axis is in thiscase, that axis parallel to the optical bench of the camera, and whichpenetrates the center of the objective lens. The Y-axis runs verticallythereto in a horizontal manner while the Z-axis stands in a verticalposition.

The alignment of that plane, for which the sums of the square of theintervals of the measured image points are at a minimum. The parametersfor this original image plane are a_(o), b_(o), d_(o), which is thengiven

    through: =a.sub.ox +b.sub.oy +d.sub.o

The determination of the distance of image b from the difference in theextension δb by focusing a specific image point at a given objectivelens pivoting angle change--in accord with the equations (5) to (7),

The determination of the distance of image b with an unpivoted objectivelens in accord with equation (8),

The determination of the z-axis parameter d_(o) by equation (9),

The computation of the set-point objective lens adjustment anglesθ_(soll), Φ_(soll) and the screen intercepts xb_(soll) with the X-axisin accord with the equations (1), (2), and (3).

The starting screen plane will be depicted in the object space. Theplane so produced, upon varied objective lens pivoting, will bere-imaged in the image space with the purpose, of aligning the newlyobtained image plane parallel to the installed screen. The necessaryobjective lens adjustment angles, θ_(soll), Φ_(soll) as well as thescreen intercept xb_(soll) which is to be included, from the screen andX-axis, yield the following: ##EQU1##

The image compensation of thin lenses serves exclusively as the physicalbasis for the above. It is yet to be proven, that the process lendsitself in a simple manner also for the application of optional objectivelenses, the optical characteristics of which may be modified throughtheir focal length as well as the positioning of their two principalplanes.

The objective lens, is now pivoted about the angles θ and Φ (in thiscase, θ=Φ=0, precisely the situation, in which the objective lens ispositioned vertically on the optical bench of the camera.) The screen isto be displaced parallely, in such a manner that it intersects theX-axis at the value xb.

Generally, also the following transformation of the input data iscarried out:

    (b.sub.i,a.sub.m,b.sub.m,θ.sub.0,φ.sub.0)→(a.sub.0,b.sub.0,d.sub.0,a.sub.m,b.sub.m,θ.sub.0,φ.sub.0)→(θ,Φ,I.sub.l)                                                    (4)

The two image equations of the original image plane and the new imageplane which come to lie in the screen, are drawn from the invariant realimage plane, on which account the two object planes are directlycorrelated. In this way, equations arise, which are not based on theprinciple of Scheimpflug, since no real image plane is defined, nor arethe equations defined for an intersecting straight line between the realand the objective planes as well as the objective and image planes.

In the relationships (1), (2) and (3), for the adjustment of the camera,the following parameters of the original image plane, the screen and theobjective lens, a_(o), b_(o), a_(m), b_(m), θ_(o), φ_(o) are quite easyto determine : a_(m), b_(m),θ_(o) and φ_(o) are available directly fromthe readout from the standard applied goniometer, and a_(o), and b_(o),from the measurement of the extension upon focusing the image point Bi.The measuring of the further parameter d_(o) of the original imageplane, however, does not evoke any insurmountable technical problems,except that the absolute value of the extension for each of the pointsBi must be defined very precisely (i.e. on the basis of 50 . . . 100 μmtolerance). Since the value of the extension length runs to as much asone meter or more, this means that the interval of the image point Bifrom the objective lens must be directly measured within a possibleerror of maximum 0.1 promille. This is indeed possible, buttechnologically somewhat involved, on which account we have developed anindirect process for the determination of the extension length.Therefore, in accord with the invention, an indirect determination ofthis parameter has been undertaken.

The fact has been made use of, that the image length b of an imagedobject point S from the objective lens changes when the lens is pivoted.The dimension of this image length variation δb depends in anunquestionable manner on the distance of the subject to lens distance sof the point S, so that the value of x can be determined from δb and theadjustment angle θ which was used. If s is known, the absolute value ofb can be determined directly from the image distance equation. Theabsolute error for the value of b lies in the general range of themeasurement error of the extension difference δb, which is very exactlydeterminable (up to ca. 50 μm) so that the relative error does notoverstep the allowable limit.

This method is particularly simple, if one only pivots the objectivelens about the Y-axis through the angle θ, (that is, I=0) and bringsinto play an object point S, which lies in the XY-plane. Then theinterval of this point from the objective lens plane is given solelythrough its image distance s and the adjustment angle θ by: ##EQU2##

Valid for the computation of the image distance b of the image point Sis: ##EQU3##

The extension difference δb (s, θ) is defined by ##EQU4##

From which is derived the following expression for the distance s of thereal subject: ##EQU5##

Only the solution employing the plus sign for the square root isrelevant, because only this yields a value s=f, which leads to a realimage of the point. The image distance of the point for θ=0, measured inrelation to the extension differential δb, can be determined from:##EQU6##

It is now possible, to produce the absolute values of all other measuredrelative extensions (i.e. the x-coordinates of the image point Bi whichis to be sharply imaged). This can be done without actually measuringany image distance directly, since the X-axis is now provided with adefined zero point. The y- and z- coordinates are simply to be derivedfrom the position of the moveable CCD chip on the screen, the X-axisposition there and the pivot angles α, β of the screen. From the nowabsolute definable intercept point of the oringinal image plane with theX- axis, x_(o), the Z-axis intercept may be found by

    d.sub.o =-a.sub.o x.sub.o                                  ( 9)

and input into the equations (1), (2), and (3).

The precision of the process can be increased even to a higher degree,in that one has not only one, but several extension differentialsmeasuring different adjustment angles θ and obtaining from these, valuesfor s.

If, during the pivoting of the objective lens, the CCD chip is alwaysmaintained, by means of appropriate motorized control, on the tie linebetween the objective lens center and the start position (θ=O ), a greatnumber of δb-values for many different values of O can be determinedduring the objective lens pivoting procedure, whereby the precisionbecomes very great for the obtained values of the subject distance.

Should the occasion arise, that no appropriate object point which liesin the XY-plane is available, naturally, any optional object point maybe used; the calculation, however, becomes a bit more complicated, sincethe interval of the point from the plane of the objective lens now alsodepends on its relationship to the Z-axis. The following equation servesthis purpose: ##EQU7## and from this: ##EQU8##

It is necessary that there are at least two values for δb upon measuringdifferent adjustment angles θ; with the readings of δb (θ) so obtained,then the equation (11), by means of variations of the free parameters sand z_(s) be applied. The parameter z_(s) is no longer needed, from s,in accord with (8), the image distance b (θ=O) can be determined. Theexactitude of the applied parameter increases, of course, with thenumber of the measured values; also, it is possible here, to carry outthe measurements very quickly by means of automatic back-check on theCCD-chip for very many values of θ.

Going from the fact, that during the determination of the extensiondifferentials, the measuring CCD must always be set at the same positionin the image, this proves useful in that one requires the completeinformation which the focusing process delivers. The process is based onthe principle, that for the observed image region, a focusing valuequantity is produced, which is dependent upon the interval of themeasuring CCD (in the x direction) from the focus and is at a maximumwhen focusing is achieved. Outside of the focus, the number is a valuefor the interval of the CCD from the focus point. If one makes the mostof this, one need only once, at the beginning, to run through the areaof the focus, in order, for the observed image region, to ascertain therun of the focus measuring numbers in dependency of the relativeposition on the X-axis. From the lessening of the focus measuring numberupon pivoting the objective lens, then the decision can quickly be maderegarding the focus and then directly on the extension difference,without being required to refocus anew from time to time. This method ofprocedure enables a quicker measuring of the extension difference fromδb in relation to the pivot angle θ of the objective lens.

The method presented here makes it possible to determine solely from theimage information, all necessary parameters. In addition, there isavoided the determination of the image distances of the focussed,repetitively given image points through direct length measurement, whichrequires much time and trouble from a technical standpoint, and hence iscostly to carry out. Instead of this, the object distance of aprincipally optional subject point is computed through the measurementof the image distance of its image point at various objective lensadjustments and from this the absolute value of the image distance isdetermined in the case of a non-pivoted objective lens. The X-axis ofthe "bench fixed" camera-coordinate system is also provided with a zeropoint, the interval of which from the objective lens is very exactlyknown and relative to this, all further extension differentials can bemeasured with a high degree of exactness. The active length capacity ofthe displacement pickup can be only a few cm long.

Additionally, all problems are avoided, which can come up upon a directinterval length determination from thermal expansion of the opticalbench or from the not entirely exact combination of a sectional opticalbank which may involve several components. It is not at all important,whether the objective lens and image standards are generally connectedwith one another. The intervals, which in the screen plane must be stilldirectly and absolutely determined (all lengths in y* and z*directions), lie in a cm-range and on this account are likewise easilydetermined by an economical motion pickup and within the required limitsof precision.

It is common knowledge, that the so-called migration of the image pointleads to undesirable perspective variation. This can be avoided byfocusing with double focus compensation, when a thin lens is pivotedaround such an axis that it intercepts the optical axis. On thisaccount, in the case of the normally available mechanical pivot axesoffset to the optical axis, virtual pivoting about the intersectingvirtual axes is carried out, for which complicated compensation pivotingand displacement are necessary. In this case, undesired migration of theobjective lens standard often occurs which leads to reaching the borderposition. Furthermore, often an undesired strong migration of the entireimage to be focused occurs in the image field of the screen.

The migration occurs in still greater magnitude for the conventionalobjective lens as installed in practice, the image scaling behavior ofwhich is described by means of good approximation by means of twoprincipal planes. In this case, exhaustive computations show thatmigration can be avoided, if the pivoting axes intersect the opticalaxis in an area centrally located between the main plane and the mainplane H'. The most favorable location of the intercept point of the axesis progressively advancing toward the main objective lens plane H' fromthe midpoint between the main plane, following the sequence: macro lens,normal objective lens II, normal objective lens I and wide angleobjective lens.

Cognizance of these facts can be used to an advantageous simplificationfor objective lens adjustment, in that each objective lens is installedin the objective lens standard in accord with its optimal pivotedposition which avoids migrations by means of an insert which holds theobjective lens entry plane satisfactorily axially disposed at thereceiving plane of the standard. By this means, with the pivoting of thestandard, each installed objective lens moves about the optimal pivotingaxis at any time without further compensation adjustments, so thatmigration is considerably reduced. The employment of this simple adapterinsert simplifies not only the adjustment of the objective lens, but italso simplifies, in many cases, the focusing of an image point when apivoting of the objective lens is undertaken.

Further, the measured differential extension values, which are of use inimage computation, are well correlated to the respective pivotingangles, an advantage which allows correspondingly exact computationresults.

The employment of the objective lens adapter insert is advantageous andinventive, independently of the use in the automatic adjustment system,since even with a manual, or semiautomatic adjustment of the objectivelens, the up to now inescapable migrationing of the image is avoidedthereby.

DESCRIPTION WITH ILLUSTRATION REFERENCES

Advantageous embodiments are presented in the FIGS. 1 to 7, wherein:

FIG. 1 shows the camera in a simplified presentation, without bellowsand with a schematic control apparatus,

FIG. 2 presents the functional dependency of the image distance on theextension difference upon various pivoting angles of an objective lenswith normalized focal length,

FIG. 3 exhibits absolute error of the focal length upon given measuringerrors for a 65 mm objective lens at varied pivoting angles,

FIG. 4 shows image distance error for a 1800 mm objective lens, and

FIGS. 5, 6 and 7 show an objective lens standard frame with variousadapter inserts.

FIG. 1 illustrates a camera with an optical bench (OB), which can alsobe assembled from several sections. Upon this, an objective lens carrier(OT) is mounted, which carries an objective lens (O), which is securedin such a manner that it can pivot about two axes (Y, Z). The pivotingangles (θ, I) are signaled to a processor (PR) by means of a goniometricpickup. If necessary, electrically controlled objective lens pivotingdrives are provided (HA, VA) which are regulated by the processor (PR).

Further, on the optical bench (OB) an image carrier (BT) is installed,to carry an image reception surface (BA), which, in like manner to thesaid objective lens, is pivotable about two axes. This reception surface(BA), during the installation has a frosted glass, i.e. a screen,inserted. Also, the pivoting angles of said reception surface and screen(α, β) are communicated to the processor (PR) as above. Further, thesepivotings are, if necessary, controllable by electrically controlleddrives.

In the image reception surface is a positionable CCD-sensor (CD), bymeans of which, when called upon, two relative positional coordinates(Y1*, Z1*) on the screen can be communicated to the processor (PR).These positional coordinates can be taken from a positioning device ofthe CCD-measuring sensor (CD). Beyond this, the CCD-measuring sensor(CD) imparts focusing relevant, image point brightness signals (SS) ofthe currently selected area to the processor (PR) for evaluation of afocus criterion in conventional manner by means of a Fourier analyzer(FA).

The image carrier (BT) is mounted axially adjustably on the bench (OB)with an extension apparatus (AA), this also providing an adjustmentsignal to the processor (PR) which is interpreted as the extensiondistance. The extension adjustment apparatus (AA) has, if necessary, anelectrically controlled drive, which is controlled by the processor(PR).

For an over view of the method of operation of the camera focusingadjustment, a Cartesian coordinate system has been drawn in, the X-axisof which runs through the principal point (H) of the objective lens (O)and parallel to the bench (OB). In case a pivotable bench is provided,the angular deviation of this with reference to the standard must betaken into consideration by an appropriate coordinate transformation.Extending upward is the Z-axis while the Y-axis extends sidewards. Inthe simplest case, three real subject points (S1, S2, S3) are to besharply imaged on the image reception surface (BA) and arranged in adefinite perspective, one to the other.

In the manual presetting by hand, the three real points (S1, S2, S3) liegenerally in a starting image surface which deviates from the screen andthe corresponding three image points (B1, B2, B3). In the example, thefirst image point (B1) with the positional coordinates (Y1*, Z1*) isfocused sharply on the screen by the sensor (CD). The second and thirdimage points, (B2, B3) lie outside of the screen.

From this originating basic positioning, in the course of the process,the focusing adjustment is undertaken. For this said adjustment,repeated extension alterations are made, with the aid of the positioningof the CCD sensor (CD), on the second image point (likewise the third)which at the start is still not sharply seen on the screen, until sharpfocus is attained. Thereby arise the extension difference data (x1-x2,x2-x3) for the position of the points in the X-direction. Now, the Y*and Z* position coordinates can be computed back to the screen, giventhe image carrier angle placements (α, β) in relative coordinates whichdescribe the inclination of the original image plane.

For the further computations, it is foreseen to undertake an imagedistance determination, for which purpose, the objective lens (O) ispivoted about a given angle (θ) and a previously sharply adjustedmeasuring point is refocused anew, whereby the distance of extensionchange (δb) is determined. With the inclusion of the objective lensfocal length (f), which is customarily transferred in electrically codedform from said lens to the processor (PR), the output signals (θ_(soll),I_(soll), xb_(soll)) ("soll" meaning "set value") which are valid forthe angular deviation of the image points into the new image planeparallel to the screen and their corresponding parallel displacement inthe X-direction, these can be computed into said plane and determined.

In FIG. 2, the dependency of the image distance (b) on the extensiondifference (δb) is illustrated. Both quantities are normalized as to thefocal length (f), whereby the graph becomes independent of (f). Thepivot angle runs (from top to bottom):

θ=2°, 5°, 7°, 10°, 15°, 20°, 25° and 30°.

The greater the pivoting angle, just so much better can the the imagedistance be determined, since a small image distance calls up a largeextension difference. If an individual value b_(f) is known, and forthis, b_(f) does not allow itself within the bounds of measurementtechnology, to be greater than 1, and this serves for the corresponding(very large) subject distance s_(f). ##EQU9## With this subjectdistance, s_(f) can be found immediately as the image distance withoutfurther measuring of the focal distance (f).

The new type of apparatus requires thus no special lineal distancemeasuring equipment for the measurement of the objective lens to thescreen interval distance. Accordingly, such an interval value or animage scale or the like are not present for input to the processor,since they have been replaced by the extension difference measurement.The means of measurement already provided were employed. The newcomputational procedure does not require the measurement of the absoluteinterval between the image points and the objective lens.

Adjustment of the angle and the extension in the data acquisitionprocedure can be carried out manually, whereby the focus value will bedisplayed by the processor, and, if required, the processor can outputelectrical positioning signals automatically. The input of the set-angleand the set-extension, i.e., the final corrected values thereof, canalso be done by hand on the basis of processor produced placementdisplays or, if desired, be done directly by electric positioning meansthrough said processor.

FIGS. 3 and 4 show error graphs for an objective lens with a 65 to 1800mm focal length, whereby an extension precision of 10 μm and an angularaccuracy of 1' are assumed. Further, a pivoting angle of θ=5°, 7°, 10°,15°, 20°, 25° and 30° have been chosen as parameters. In the case ofsizable pivoting angles, error, even in the case of large focal lengthsis held at a low value. Since, however, relatively large extensionlengths are to be measured in these procedures, it has provedadvantageous, if, using the extension distance (AW) which said distancecan be found with the required precision in accord with measurementtechnology, the x-coordinate determinations are taken therefromemploying a combination of a roughly incremental sample, but an exactstandard of measurement. For this purpose, the optical bench (03), FIG.1, is provided with a mechanical incremental means, i.e. a regularlyperforated, linear raster (L1-L2) that serves the incrementally exactpositioning of the objective lens carrier (OT) and the image carrier(BT) on said optical bench by pin insertion.

Also, several bench sections (OB1, OB2) may be incrementally exactlylinked together by means of pin insertion in the perforated segments.The x-coordinate determination is done thus, first as shown with arelatively large error, whereafter a resetting into the next neighboringincremental section is made and, in the corresponding raster measurementthe remainder from the found raster point is added on, so that theabsolute total error is only a little larger than that of the extensiondistance. This also permits working with small pivoting angles θ in thecase of small extension distances, whereby, in spite of all, a highprecision of the image distance determination is achieved.

The raster length will, in practice, be chosen smaller than the lengthof the extension distance, and a multiple greater than the greatestabsolute error, which arises upon a given pivoting angle.

Through the hole and pin raster, there arises another alternative forindirect image distance or scale determination, in that the objectivelens carrier (OT) is displaced by at least one increment length andbefore and after a focus point of a real point is made, whereby theextension length is ascertained.

The incremental divider on the optical bench and the related incrementaldevices on the standards and the bench connections are advantageousdevelopments of the camera arrangement for the application of the of thenew process of focusing placement.

As already mentioned, the given formulae extend themselves in the caseof objective lenses with several principal planes. Besides this, it mustbe taken into consideration that the pivoting of the objective lens isoften not about a principal plane axis, but parallely offset therefrom.By means of the interval d_(h) the principal plane yields a paralleloffset h to the image plane in the direction out from the objective lensfrom the relationship h=d_(h) cos α

From this, can be evolved the parameter of the displaced image plane:##EQU10##

By conversion computing to the pivot point coordinate system, theparameters-of which are indicated with the raised "h" index, and uponintroduction of the set-point objective lens pivot angle, there isobtained the extension adjustment for the doubled focus placement asseen in: ##EQU11## and for the Z-axis section:

    d.sub.m.sup.v =d.sub.m.sup.H +a.sub.m A.sub.1 cos φ.sub.p cos θ.sub.p +b.sub.m A.sub.1 sin θ.sub.p cos θ.sub.p -a.sub.l sin θ.sub.p                                (15)

Wherein, A₁ is a displacement parameter and wherein the index sub "p"always represents the "set point" index in other equations.

In the above, various methods of solving are presented for thecomputation of the set-point adjustment value. In the case of thegreatest simplification of the formulae, which are valid for the thinlenses, the differential relationship of the extension distance to aobjective lens pivoting angle alteration is brought into the equationsand a final solution for the sought after set-point position valueresults.

If more complex equations are applied, which produce a more exactdefinition of the image system, then two kinds of considerations for thesolution of the equations appear. In the case of one method, for therelated parameter pairs of the extension upon focusing, that is, thestart extension and the start pivoting angle, are brought, asindeterminate quantities into a first equation system. The finalextension, which is defined from the indeterminate values and theextension change, along with the final pivoting angle, is input into asecond equation system. Then, by setting the two systems equal to oneanother, the indeterminate quantities eliminate themselves and theequations, because of their complexity cannot be normally solved, but inaccord with known iteration methods the set points can be found. Theequivalence setting of the two image side parts of the equation systemsis possible, because the two object side portions of the equationsystems in relation to the adjustment changing are invariant.

A further method does not proceed from two approaches together with therelated equation systems, but from an entirely different point of viewof the image equation system. The evolved results and the equationsregarding the parameters to be varied, i.e. that of the variationdependent parameters, yield further equations, with the inserted realquantities of the measured dependencies, which equations are to besolved by the iteration method, in such a manner that the soughtset-point values are found.

The determination of the mutual dependencies of the objective lensadjustment to the extension changes at any given time upon focusing, istechnologically very simple to bring about without giving rise to imagemigrations.

This is the case when the objective lens is pivoted about a clearlydefined pivoting axis which intersects with the optical axis at adefinite point or in a closely localized zone. This zone lies, accordingto the type of objective lens, midway between the principal planes up tothe plane H' and, is determinable for the conventional installation ofan objective lens. The pivoting of the objective lens can be made aboutthe optimal axis, when the said optimal axis does not coincide with themechanical pivoting axis. This is accomplished by means of appropriatecompensation displacements virtually about the optimal axis, whichrequires, however, corresponding calculation of the compensationdisplacement and related means of positional adjustment.

A particularly simple adjustability of the objective lens arises, whenthe optimal angular displacement axes coincide with the mechanicalpivoting axes. To this end, the mechanical pivoting axes must meet withthe optical axis at one point, and the objective lens must be so set inthe objective lens standard, that its optimal pivoting axes conform withthe mechanical pivoting axes.

As may be inferred from FIGS. 5, 6, and 7, it is advantageouslyarranged, that between the lens holding elements (HR) of the objectivelens holder (OT) currently an adapter set (E1-E3) is installed, so thatthe framing reference surface (SOS) exhibits a definite axial backstopto the current objective lens reference surface (BF01-BF03) and inaccord with this, the pivoting axis (Y) of the objective lens carrier(OT) lies properly in the objective lens.

In the case of the first adapter (E1) in FIG. 5, the objective lens isdisplaced in the direction of the subject. Where the second adapter (E2)is concerned, there is no axial positioning beyond the customaryplacement. In the third adapter (E3) arrangement, the objective lens ismoved toward the screen. The various adapter inserts (E1, E2, E3) arethus flat or extend themselves inward or outward from the retainingframe (HR).

The understanding that the exceptional focussing, which is in accordwith the purpose of the invention, of an already, prealigned, partiallyfocussed image, requires only a refocussing of the camera withinconfined limits, was made use of. That is, in accord with the invention,subsequent to the determination of the gradients of the positioningparameters, with the aid of these said gradients, the necessary furtherparameters are solved for through iterative computation. In thisprocess, and in a provable manner, a satisfactory precision is achieved.

The utmost sharp focussing, in accord with the process, now permits, ashas been shown, the use of optimal aperture openings, which are chosen,on the one hand, to correlate the required depth of focus at moderatelight requirement and on the other hand to avoid extensive diffractionblurring.

I claim:
 1. A focusing process for a camera;having an objective lenscarrier (OT) and an image carrier (BT), which are maintainedpositionally relative to one another in a straight line optical benchdirection (X) in which the spatial interval (x1-x2, x2-x3, δb)betweenthem is variable, wherein the said interval changes are signaled to amicroprocessor (PR), equipping the objective lens carrier (OT) with anobjective lens (O) secured to pivot about two axes (Y, Z), said axesbeing perpendicular to one another and to an optical bench direction(X), two respective objective lens angles (θ, Φ) and a focal length (f)of said objective lens being inputted to the microprocessor (PR), theimage carrier (BT) having a frosted glass plate image screen (BA), saidscreen being moveable about the two axes (Y, Z) perpendicularly disposedto one another and to the direction of the bench direction (X), and tworespective image reception angles (α, β) thereof being sent to themicroprocessor (PR), the image screen (BA) having a focusing adjustmentsensor (CD), which signals a degree of focus, and is positionable in twoimage reception coordinates (Y1*, Z1*) which, together with a focusvalue, are inputted to the microprocessor (PR), further possessing atleast three select image point areas (B1, B2, B3), which lie in asecondary image plane for the simultaneous adjustment of a focus havingsaid image point areas and the focus adjustment sensor (CD) on the imagescreen (BA) subjected to determination of their respective image screencoordinates by means of a change in the interval between the imagecarrier (BT) and the objective lens (O) sequentially at a current timefor each area of said image point areas through focus adjustment bymeans of the determination of the related screen coordinates (Y2*, Z2*,Y3*, Z3*), and said positional changes of the image carrier (BT), thesebeing (x1-2x, x2-x3) and being inputted to the microprocessor,obtaining, by means of input data collected from the microprocessor (PR)a determination of the positional parameters (a_(o), b_(o), a_(m),b_(m), θ_(o), Φ_(o)) of the image screen (BA) as well as of thesecondary image from which, together with a further image parameternecessary for computation, this latter originating in the solution ofimage equations, calculating such set point adjustment values (θ_(soll),Φ_(soll)) suitable for the pivoting of the objective lens carrier (OT)along with a value for the adjustment of the interval between the imagecarrier (BT) and the objective carrier (OT), and the results thereofbeing made available, so that the new image plane adjusted by theseset-point values (θ_(soll), Φ_(soll), xb_(soll)) comes as close aspossible to coinciding with the image screen (BA), thereincharacterized, in that one of the objective lens focusing adjustmentparameters (θ, Φ, axial displacement) is altered by a predeterminedamount, thus allowing a condition wherein, for a selected image point,can be measured an extension difference, which distance is determined byan extension apparatus AA in the bench direction (X) and a first set ofthe image equations with the input of the original objective lensadjustment parameters and an undetermined image distance (b) as well asa further set of image equations with the input of varied objective lensparameters (θ, Φ) and compensated by the image distance (b), changed byan extension difference (δb) and permitting determination of the setpoint values (θ_(soll), Φ_(soll), xb_(soll)), functional derivations ofthe image equations having been created in regard to the objective lensfocusing parameters (θ, Φ, axial displacement) and in regard to thecurrent image distance (b) in accord with the focus at the time and thethereby arrived at focus change (θ, Φ, axial displacement) and themeasured extension difference (δb), being inputted to the saidderivations and solved for the set point signals (θ_(soll), Φ_(soll),xb_(soll)).
 2. A process in accord with claim 1, therein characterized,in that the selected image point, where the objective lens (O) has notbeen pivoted about the horizontal axis (Y) and lies in the horizontalXY-plane and the pivoting of the objective lens (O) takes place aboutthe said horizontal axis (Y) by a predetermined pivoting angle (θ) forthe determination of the extension difference.
 3. A process in accordwith claim 1, therein characterized, in that the selected image point,is focussed by at least two pivoting angles and thereby the extensiondifferences (AW) are measured and from a related equation (11) by meansof which, through parameters, a real object distance (S) and therefromthe image distance (b) is calculated, which are inputted to the imageequations for the solution thereof.
 4. A process in accord with claim 1,therein characterized, in that during an extension change, the currentincremental extension changes from the image point signals (SS) of thecorresponding focussing values of the selected image point arecontinually monitored and correspondingly stored in the microprocessor(PR) memory, and subsequent to the pivoting of the objective lens aboutthe predetermined pivoting angle (θ), or after an objective lensdisplacement along given axial movement path, from the then producedimage point signals (SS) the focus value is determined and, now havingthis value, from the stored data, the corresponding extension change(δb) is sought out, which serves for further computations.
 5. A processin accord with claim 1 therein characterized, in that the image distance(b) is first approximated from the extension difference (δb) and theclosest related raster incremental interval of the image carrier (BT) ofa linear bench raster (L1-LN) from the objective lens carrier (OT) isdetermined to this so attained raster interval the extensiondifferential, also corresponding to the raster, is added and this socomputed image carrier-objective lens carrier interval is used for amore exact further image parameter in sequential computations.
 6. Aprocess in accord with one of the claims 1, 4 or 5, thereincharacterized, in that the objective lens displacement path amounts toone or more to the bench raster lengths.
 7. A process in accord withclaim 1 therein characterized, in that by means of image equations, thestart image plane (B1, B2, B3) in the image space is on a new imageplane, which is parallel to the image screen (BA), and will be broughtback and the objective lens angles (θ_(soll), Φ_(soll)) and subsequentlythe inserted intersection point (xb_(soll)) of the image reception plane(BA) is calculated with the X-axis.
 8. A process in accord with claim 1therein characterized, in that a parallel insert (h) of the image plane,dependent on a main lens plane interval (d_(h)) of the objective lensand an insert of the objective lens pivoting axis intersection point forthe principal plane thereof, is taken into consideration in thecomputation for the set-point values (θ_(soll), Φ_(soll), xb_(soll)). 9.A camera for application with a focusing process in accord with claim 1therein characterized, in that the bench thereof (OB) is provided with araster with mechanical increments, in particular, hole and spaceincrements, (L1-LN) and the objective lens carrier (OT) and the imagecarrier (BT) with raster apparatus are secured incrementally exact toone another in the said raster with appropriate means, namely rasterpins.
 10. A camera in accord with claim 9, therein characterized, inthat the optical bench (OB) is comprised of at least two bench sections(OB1, OB2), which are joined in exact incremental exactness by aconnection piece possessing a raster apparatus for the given raster. 11.A camera in accord with claim 9, therein characterized in that theraster length is shorter than a maximum extension path length.
 12. Acamera for application with a focusing process in accord with claim 1therein characterized, in that the objective lens (O) is so placed inthe objective lens carrier (OT), that the pivoting axes (Y, Z) of saidlens intersect at a point and the point of intersection lies between thetwo principle planes (H, H') of the objective lens (O) .
 13. A camera,in accord with claim 12, therein characterized in that the intersectionpoint for the axes (X, Y, Z) lies between the midpoint and the principalplane (H'), which said midpoint lies between the two principal planes(H, H').
 14. A camera in accord with claim 12, therein characterized inthat between the objective lens carrier (OT) and the objective lens (O),a corresponding and suitable insert (E1, E2, E3), which possesses anaxial partition between the image reception surfaces (BF01, BF02, BF03,SOS) of the objective lens (O) and the objective carrier (OT), is placedin such a manner that the intersection point of the axes (X, Y, Z) isfound in the optimal axial position for the objective lens (O) beingused at that time and said point is between the principal planes (H,H').